1020 



SCAXDIXAVIAN FISIIE.S. 



apjieanirice, ot loljiilalc arf/aiis (S\v. fiikorc/aii, Germ. 

 Lappenorgan). They cc^nsist of a ro\v of rounded la- 

 mella', coherent to each other just at the base, and 

 suspended from the ett'erent duct (y;a,s deferens). 



In their internal structure the ovaries show a mcsh- 

 woi'k (if connective tissue, so closely packed, when they 

 are unripe, with strongly refractive fat-globules, that it 

 is dilticult enough to distinguish among these the ex- 

 ceedingly small eggs, wliich iu tlie common Eel usually 

 measure during the sunnner months at most about '/lo 

 mm. in diameter, and late in autumn or even in De- 

 cember attain a size of abcnit ' ., mm. The testes are 

 essentially similar to the ovaries in the texture of their 

 stronui (connective-tissue fold), but arc witliout adiposis, 

 being consequently more transparent and difficult of 

 detection. Most easily perceptible is their white ett'erent 

 duct {ras deferens). Their seminal cells (spermatogonia) 

 are also exactly similar at first to newly-formed ova, 

 and remain extremely small, measuring 0.015 — 0.03 

 nun. in diameter; but they multiply by fission as thej' 

 pass from the germinal epithelium into the stroma, 

 where they gather in their special cavities (spermatic 

 ducts). In the Conger and Mura^na the development of 

 the spermatozoa has been traced; in the common Eel 

 spermatozoa have not yet been observed. 



Some Enchelymorphs, among them pi'obably our 

 common Eel", cleve]o|) without any great metamorphosis. 

 Others, such as the Conger, have a larval existence dur- 

 ing which they are scarcely recognisable. These larvae 

 were first described under a generic name, Lepfoceplta- 

 Jhs'' or Helmichtliys' \ and were long regarded as types 

 of a distinct family Leptocephalida or Helniichthyidce) 

 or even of an order {Lemniscafi''). The structure of 

 these larva; was described by Kollikeh in 1852'. They 

 are thin (ribbon-shaped) or more terete (cylindrical), 

 and so transparent that only the black eyes -with sil- 

 very iris betray their ])resence, as thej' move with slow 

 and languid undulations of their wliole body, sometimes 



near tlie coast, sometimes in the middle of the ocean. 

 The head is extremely small — hence their name' — 

 and the skeleton most feebly developed, ^vith hardly 

 anj^ signs of vertebrae, these being confined, as a rule, 

 to the hindmost part of the body. The notochord 

 {clHirda dorsaJis), entire or only marked witli annular 

 constrictions, advances without a break into tlie carti- 

 laginous mass of the skull, and lies in the body, en- 

 closed, together witli tlie sjiinal cord and the great 

 blood-vessels, in a nmcous mass, which separates these 

 parts from the surrounding musculature. The muscular 

 mass is fastened to the skeleton only in front (at the 

 head) and behind (at the tail), lieing attached elsewhere 

 to the skin; but it is divided, as in other fishes, by 

 the zigzag transverse bands (myocommata) into flakes 

 (myomeres), each with an angle (directed forwards) 

 at the middle of the sides of the body, another (di- 

 rected backwards) at the back, and a tliird at the 

 ventral margin. The mt)utii is armed, liotli in the 

 upper jaw and the lower, \vith comparatively large and 

 strong, rather scattered, straight and pointed teetli, set 

 in a single row and directed ol)li(|nclv forwards. Each 

 nasal cavity is a depression in front of the eye, with- 

 out proal nostril. The tul)ular abdominal cavity ex- 

 tends along the greater part of the ventral margin. 

 The straight digestive canal includes, according to Kol- 

 LiKER, a cacum-like stomacii, with two upward, ca^'ai 

 diverticula and Uvo similar ai)i)endages belonging to 

 the intestine. The liver is faintly developed; spleen, 

 air-bladder, and sexual organs are wanting. From this 

 larval structure Facciola" has succeeded in tracing a se- 

 ries of transition-forms that bring it to perfect identity 

 with the young of the Congers, a metamorphosis at 

 which Gjll'' had already hinted. The most singular 

 point is, however, that these larva>, retaining the struc- 

 ture proper to their first stage of development, can 

 attain dimensions considerably greater than those of' 

 the stages in which the terete type and internal struc- 



" In the Ball. Aocad. Gioeu. Sc. Nat. Catania (Fasc. 34 — 35; Nov. 1893 t- (ieim. 1.S94, p. 4) Grassi and Calanphuccio have ex- 

 pressed the supposition that the ova of Am/iiilla vulgaris are to he t'omid Hoatins in (lie sea, aud that Leptncephahis bveiirflstns is the 

 larval stage of tliis species. 



'' Gronovii Zooplii/tac, Fase. I (17ri3), \>. 135. Morris, an aiHiuaintanc-e of Pkn.nan'i's. had foimd Uiese Hshes in St. George's Chan- 

 ni-1, ..ti Holyhead, North Wales. 



"' Rakinesquk, Ind. Itliol. Sic, where the name is, however, written Heliiiictis. 



'' Richardson. 



' Zeltschr. f. Wiss. Zool., Bd IV. p. 360. 



-' From Gr. kerctog, fine, small, and y.erpah'j. heail. 



" II Natnralista Sieiliano, Anno XII (1893), p. 194. 



'' Proc. Aead. Nat. Se. Philad. 1864, p. 207. 



